1. Field of the Invention
The present invention relates to a liquid crystal display device (LCD), and more particularly, to a brightness-enhancing light guiding plate, which changes an optical distribution concentrated on a limited surface area into a uniform optical distribution on an enlarged surface area and thus enhances a brightness necessary for displaying an image, thereby improving a displaying performance, and an LCD device using the same.
2. Description of the Related Art
Generally, an LCD can be defined as one of display devices for displaying an image using an electro-optical property of liquid crystal having a physical property between crystal and liquid.
Herein, the electro-optical property of the liquid crystal is meant by that, when an electric field is applied to the liquid crystal, an alignment of liquid crystal molecules is changed and thus an amount of light passing through the liquid crystal is changed.
The liquid crystal having the aforementioned property, however, cannot generate light by itself. Thus, in order to perform a displaying operation in the LCD, the liquid crystal should be precisely controlled in a minute surface area unit and light capable of passing through the liquid crystal should be available.
The precise control of the liquid crystal is realized by a thin film transistor fabricated in a very small size by a semiconductor device fabricating process, and a transparent electrode having a high transparency for light transmission and a desired conductivity.
Further, light can be provided to the LCD by a backlight assembly. Since the displaying operation in the LCD is generally performed in a plane form, the backlight assembly has to generate an artificial light having a uniform optical distribution in the plane shape.
Compared with the sunlight, the artificial light source is, however, in the form of a point light source or a linear light source. The point light source and the linear light source have a problem in that brightness thereof is abruptly changed depending on a change in a distance from the light sources.
Therefore, it is very difficult to directly apply the point light source or the linear light source to the LCD without carrying out a separate light processing operation.
Recently, in order to overcome the foregoing problem, there has been developed a technology for changing the point light source or the linear light source into the plane light source. A light guiding plate (LGP) is used for changing the point light source or the linear light source into the plane light source.
As an example, the LGP may have a rectangular parallelepiped shape. A light is incident into a side surface of the LGP. The incident light is reflected by a bottom surface of the LGP and widely spread, to be outputted from the LGP. In other words, the LGP functions to improve the optical distribution, and at the same time, to change a direction of the light. In order to enhance the reflection efficiency, reflection dots including a reflective material with a superior reflectivity are formed on the bottom surface of the LGP.
The reflection dots are generally formed by a silkscreen method or the like. If the reflection dot does not have a desirable shape, the light reflection efficiency may be lowered. Further, it is difficult to form the reflection dots in a critical size or less by the silkscreen method.
Therefore, a light guiding plate without the reflection dots is needed for the purpose of high brightness displaying operation.
The present invention provides a brightness-enhancing light guiding plate capable of increasing efficiency in using a light generated from a light source and thereby capable of carrying out a high brightness displaying operation.
Further, the present invention provides an LCD using the brightness-enhancing light guiding plate capable of increasing the efficiency in using the light generated from the light source and thereby capable of carrying out the high brightness displaying operation.
In one aspect, there is provided a brightness-enhancing light guiding plate. In the brightness-enhancing light guiding plate, a light is incident through a light incident surface. A bottom surface is arranged adjacent to the light incident surface, and reflects the light. A light output surface faces the bottom surface. The light is outputted through the light output surface. A brightness-enhancing recess portion has a reflection recess surface which faces the light incident surface with a first inclination with respect to the bottom surface and reflects the light toward the light output surface, and a non-reflection recess surface which is extended from an end of the reflection recess surface with a second inclination with respect to the bottom surface. The second inclination of the non-reflection recess surface is greater than the first inclination of the reflection recess surface.
In another aspect, there is provided a liquid crystal display. The liquid crystal display includes a backlight assembly. The back light assembly includes a brightness-enhancing light guiding plate. In the brightness-enhancing light guiding plate, a light is incident through a light incident surface. A bottom surface is arranged adjacent to the light incident surface, and reflects the light. A light output surface faces the bottom surface. The light is output through the light output surface. A brightness-enhancing recess portion has a reflection recess surface which faces the light incident surface with a first inclination with respect to the bottom surface and reflects the light toward the light output surface, and a non-reflection recess surface which is extended from an end of the reflection recess surface with a second inclination with respect to the bottom surface. The second inclination of the non-reflection recess surface is greater than the first inclination of the reflection recess surface. The backlight assembly also includes an optical distribution changing part for making uniform an optical distribution of the light outputted from the brightness-enhancing light guiding plate. An LCD panel assembly precisely controls light amount of the light generated from the backlight assembly to display an image.